v3.7.0.1
Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Environmental Matters Details [Line Items]    
Environmental Exit Costs, Reasonably Possible Additional Loss $ 71  
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 98 $ 94
Provisions/adjustments 6 10
Cash reductions (6) (3)
Ending balance 98 101
Duke Energy Carolinas [Member]    
Environmental Matters Details [Line Items]    
Environmental Exit Costs, Reasonably Possible Additional Loss 22  
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 10 10
Provisions/adjustments 1 2
Cash reductions 0 (1)
Ending balance 11 11
Progress Energy [Member]    
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 18 17
Provisions/adjustments   1
Cash reductions (1) (2)
Ending balance 17 16
Duke Energy Progress [Member]    
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 3 3
Cash reductions 0 (1)
Ending balance 3 2
Duke Energy Florida [Member]    
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 14 14
Provisions/adjustments 1 1
Cash reductions (1) (1)
Ending balance 14 14
Duke Energy Ohio [Member]    
Environmental Matters Details [Line Items]    
Environmental Exit Costs, Reasonably Possible Additional Loss 36  
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 59 54
Provisions/adjustments 4  
Cash reductions (4)  
Ending balance 59 54
Duke Energy Indiana [Member]    
Environmental Matters Details [Line Items]    
Environmental Exit Costs, Reasonably Possible Additional Loss 7  
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 10 12
Provisions/adjustments (1) 6
Cash reductions 0  
Ending balance 9 18
Piedmont Natural Gas [Member]    
Environmental Matters Details [Line Items]    
Environmental Exit Costs, Reasonably Possible Additional Loss 2  
Accrual for Environmental Loss Contingencies [Roll Forward]    
Beginning balance 1 1
Provisions/adjustments 1  
Cash reductions 0  
Ending balance $ 2 $ 1